Cap Polyposis—A Rare Cause of Rectal Bleeding in a Young Woman

ABSTRACT Cap polyposis is a very rare clinical entity, with only few cases reported in the literature. It is a benign disease, characterized by inflammatory polyps of the gastrointestinal tract. A 35-year-old woman was referred to our Gastroenterology department due to rectal bleeding. Endoscopic examination revealed multiple polypoid lesions in the middle/lower rectum. Histology was compatible with cap polyposis. She underwent mucosectomy of the lesions, with clinical and endoscopic improvement. Clinical findings and therapeutic approach represent a challenge in this pathology.


INTRODUCTION
Cap polyposis is a clinical entity first described more than 20 years ago, although it is still a very unrecognized disease.Few cases have been described worldwide, and many are misinterpreted as an inflammatory bowel disease, leading to prolonged and ineffective treatments.Given its rarity, the clinical findings and therapeutic approach remain a challenge.

CASE REPORT
A 35-year-old woman was referred to our Gastroenterology department due to rectal bleeding, anemia, and a rectal mass on digital examination.She had an unremarkable medical history besides chronic constipation.She was submitted to an ileocolonoscopy, with the identification of multiple polypoid lesions in the middle/lower rectum and anal canal (Figure 1).Biopsies revealed inflammatory pseudopolyps, absence of malignancy, and focal positive immunohistochemical stain for cytomegalovirus (CMV) (Figure 2).Serology for CMV demonstrated a positive test for IgG and negative for IgM.She was treated with intravenous ganciclovir without significant improvement of symptoms.Blood analysis revealed severe anemia and hypoalbuminemia.Electrolytes, liver enzymes, immunoglobulins, complement, autoantibodies, calprotectin, inflammatory markers, and tumoral markers were within the reference range.Chlamydia trachomatis, Neisseria gonorrhoeae, HIV, Treponema pallidum, and hepatitis B and C were negative.Table 1 presents a summary of the laboratory and infectious panel.An abdominal and pelvic computed axial tomography scan was performed, describing a thickened rectal wall without other abnormalities.Upper endoscopy was normal, and gastric biopsies were positive for Helicobacter pylori.Eradication therapy was prescribed, and a following urea breath test was negative.Four months after, colonoscopy was repeated to perform biopsies which revealed an ulcerated proctitis without malignancy and without positivity to CMV or other infections pathogens.The patient presented with clinical deterioration, with frequent rectal bleeding, severe anemia treated with red cell blood transfusion, and persistent hypoalbuminemia.At that point, it was decided to proceed to the endoscopic removal of the majority of the rectal polyps with mucosectomy and the lesions of the anal canal with transanal excision surgery.Histology identified elongated serpiginous crypts and a "cap" of inflammatory granulation tissue with fibrinopurulent exudate, compatible with "cap polyposis" (Figure 3).The anal canal lesions were classified histologically as inflammatory cloacogenic polyps (Figure 4).At 2-month follow-up, she was almost asymptomatic, her hemoglobin levels normalized and with no endoscopic relapse (Figure 5).

DISCUSSION
Cap polyposis is a benign disease of the colon characterized by inflammatory polyps, typically located at the apex of mucosal folds.It was described for the first time in 1985, 1 and since then, less than 100 cases have been described worldwide.
This disease is more frequent in adult patients, but there were case reports in pediatric patients.The median age at diagnosis is 52 years, and it has a slight female preponderance. 1,2e most important differential diagnoses are malignant neoplasms of the gastrointestinal tract and inflammatory bowel disease.[3] The etiological mechanism of the disease is unknown, although mechanical, inflammatory, or infectious causes have been proposed.This clinical entity presents histopathological similarities with prolapse mucosal syndrome, and it is proposed that it may derive from an intestinal motility disorder.Prolapse of the rectal mucosal folds, secondary to excessive straining at defecation, can lead to the appearance of polypoid lesions and their mucous lining.The fact that these polyps are more common in the distal colon, the symptomatic improvement after avoiding severe straining at defecation and the high prevalence of constipation in this group of patients support this mechanical etiological hypothesis. 4,5 infectious cause is proposed as a possible etiological factor.Cases of regression have been described after antibiotic therapy with metronidazole in monotherapy.There is a strong association between "cap polyposis" and H. pylori infection, although the bacteria has never been detected in the colonic mucosa.This finding raises the question of whether eradication therapy   influences reduction in lesion burden by direct elimination of the bacteria or whether this occurs as an indirect effect on intestinal microbiota. 6,7One case report demonstrated that antibiotic treatment led to regression of cap polyposis through significant alterations in fecal microbiota composition and that microbiome-targeted therapy may be useful in this disorder. 8ere are no specific diagnosis criteria.It is based on clinical, endoscopic, and histological findings.The most common symptoms are mucous discharge, diarrhea, rectal bleeding, abdominal pain, and tenesmus. 1Serum albumin levels are often low, and it has been described an association with proteinlosing enteropathy.There are 2 cases in the literature associating cap polyposis with this entity, with one of them suggesting a protein loss directly from the polyps.The diagnosis was made with technetium-labeled human albumin scintigraphy, and it has been considered the gold-standard investigation. 5,9,10Serum inflammatory markers are usually within reference values, and extraintestinal manifestations are rare.
The typical endoscopic appearance is the presence of polypoid lesions coated with a fibrinopurulent exudate.Polyps can vary in size, morphology, location, and number. 1 The most common location is within the distal portion of the gastrointestinal tract, mostly the sigmoid colon and rectum. 92][13] Polyps present histologically with hyperplastic, tortuous, elongated crypts with an inflammatory infiltrate in the lamina propria.The surface is ulcerated and covered with a fibrinopurulent exudate. 1 There is still no well-established therapeutic approach since the etiology remains undetermined.The use of corticosteroids, aminosalicylates, infliximab, and antibiotics, such as metronidazole, has been described.H. pylori eradication therapy is also recommended when positive. 2,11,14,15Endoscopic resection of polypoid lesions seems to be the most effective therapeutic measure in controlling symptoms, although recurrence is frequent.The most used technique is mucosectomy, although there is a reported case of submucosal dissection. 7In refractory cases, surgical resection of the affected colon or even total colectomy may be considered. 1 Patients should implement behavioral modification strategies, such as the use of laxatives and avoidance of straining at defecation. 14oacogenic polyps are benign lesions that belong to the "mucosal prolapse syndrome" and are therefore associated with excessive straining at defecation.It comprehends multiple clinical entities such as solitary rectal ulcer syndrome, prolapsing mucosal polyps, and cap polyposis. 16They are typically found at the anorectal junction, although they can be identified throughout the colon. 17Unlike cap polyposis, cases of malignant transformation have been described. 18

Figure 1 .
Figure 1.Ileocolonoscopy.Multiple polypoid lesions in the middle/lower rectum, covered by fibrous mucus (A, B, and C).Multiple large polyps, located at the anorectal junction, and prolapsing exteriorly through the anal canal (D).

Figure 4 .
Figure 4. Rectal polyp (hematoxylin-eosin, 603).Polypoid lesion with verticalization of muscularis mucosa muscle fibers and accompanying dilated venous blood vessels, suggesting a prolapse-type lesion of the juxta-anal rectal mucosa.In this section, partial erosion is identified.

Figure 5 .
Figure 5. Retossigmoidoscopy.The mucosa presents a scarring pattern in relation to previous endoscopic therapy, but without evidence of recurrence.